USPTO Patents Application 10687850

(19)

J

Europaisches Patentamt
European Patent Office
Office euro pee n des brevets

(11)

EP1 130 390 A1

(12)

EUROPEAN PATENT APPLICATION

published in accordance with Art. 158(3) EPC

(43) Date of publication:

05.09.2001 Bulletin 2001/36

(21) Application number: 00957017.7

(22) Date of filing: 07.09.2000

(51) Int CI 7: G01N 27/447, C12Q 1/00,
C12N 9/00

(86) International application number:
PCT/JP00/06111

(87) International publication number:

WO 01/20316 (22.03.2001 Gazette 2001/12)

(84) Designated Contracting States:

• YOSHIOKA, Toshihiko

AT BE CH CY DE DK ES Fl FR GB GR IE IT LI LU

Hirakata-shl, Osaka 573-0035 (JP)

MC NL PT SE

• NANKAI, Shiro

Designated Extension States:

Hirakata-shl, Osaka 573-0071 (JP)

AL LT LV MK RO SI

• MIYAMOTO, Yoshlko

Suita-shi, Osaka 565-0821 (JP)

(30) Priority: 13.09.1999 JP 25957999

(71 ) Applicant: MATSUSHITA ELECTRIC INDUSTRIAL

(74) Representative: Nachshen, Neil Jacob et al

D Young & Co

CO., LTD.

21 New Fetter Lane

Kadoma-shi, Osaka 571 -8501 ( JP)

London EC4A 1 DA (GB)

(72) Inventors:

• TSU Jl, Satoko

Katano-shi, Osaka 576-0036 (JP)

(54) PROCESS FOR PRODUCING LIPID-MODIFIED ENZYME AND BIOSENSOR

(57) The present invention provides a biosensor capable of accurately measuring the concentration of a substrate,
such as glucose, with high storage reliability.

A method for producing a lipid-modified enzyme of the present invention includes the steps of: adding an enzyme
to a medium containing a lipid represented by the following formula (1) so as to produce a complex of the lipid and
enzyme; precipitating the produced complex; and drying the precipitate. A biosensor according to the present invention
comprises an electrode system including a working electrode and a counter electrode formed on an electrically insu-
lating base plate; and a reaction layer formed on or in the vicinity of the electrode system, and the reaction layer includes
at least two layers: a layer containing a lipid-modified enzyme obtained by the above method and a layer containing
an electron mediator.

n* r

CnH2n+i / CH3

(1)

o

CO

wherein each of m and n is independently an integer between 14 and 18, and X" is Ch, Br, r, H 2 P0 4 -, HS0 4 -,
CO orN °3-

Q.
UJ

Printed by Jouve, 75O01 PARIS (FR)

(Cont next page)

Ulfe.

EP1 130 390 A1

Description

Technical Field

[0001] The present invention relates to a biosensor capable of rapidly and readily quantifying a substrate (specific
component) contained in samples such as biological samples, like blood and urine, raw materials and products in the
food industry and fruit juice, with high accuracy, and also relates to a method for producing a lipid-modified enzyme
for use in the biosensor.

Background Art

[0002] There have been proposed biosensors that readily quantify a specific component (substrate) in biological
samples and foodstuffs without diluting and stirring the sample solutions. Japanese Laid-Open Patent Publication No.
Hei 3-202764 discloses one example of biosensor in which an electrode system is formed on an insulating base plate
by a method such as screen printing and a reaction layer containing an oxidoreductase and an electron mediator
(electron acceptor) is formed on this electrode system.

[0003J This biosensor quantifies the concentration of the substrate in the sample as follows.
[0004J First, the sample solution is dropped on the reaction layer of the biosensor to dissolve the reaction layer and
an enzyme reaction proceeds between the substrate in the sample solution and the oxidoreductase in the reaction
layer. The electron mediator is reduced in association with this enzyme reaction. After elapse of a certain period of
time, a voltage is applied to the electrodes of the sensor to electrochemically oxidize the reduced electron mediator,
and the concentration of the substrate in the sample solution can be quantified from an oxidation current value obtained
in the oxidation.

[0005] A biosensor using a lipid-modified enzyme is disclosed in Japanese Laid-Open Patent Publication No. Hei
7-110313. By modifying an enzyme with a lipid, the enzyme becomes insoluble in water but soluble in an organic
solvent, thereby allowing the formation of the reaction layer in a state separated from the water-soluble electron me-
diator. It is therefore possible to provide a rapid and highly reliable sensor.

[0006] In biosensors with conventional structures using no lipid-modified enzyme, since the enzyme and electron
mediator are present in a single reaction layer, there is an advantage that a reaction is promptly initiated upon supply
of the sample solution. However, when the enzyme is stored in a mixed state with a compound such as an electron
mediator for a long period of time, the activity of the enzyme is lowered, resulting in a problem that the response
characteristics of the sensors are impaired. There is also a problem that an oxidation current value (blank value) is
given for a sample solution containing no substrate. Then, a structure for separating the enzyme and the electron
mediator into different layers was considered, but since the enzyme and the electron mediator were both soluble in
water, it was difficult to bring them into perfectly separated states.

[0007] Meanwhile, as a method for producing a lipid-modified enzyme, a method of mixing a specific lipid dispersion
and enzyme solution was proposed (Thin Solid Films, 180. p65 (1989)). However, it was difficult to obtain a highly
active lipid-modified enzyme with a high yield.

[0008] An object of the present invention is to solve problems as mentioned above while utilizing the advantageous
features of biosensors of conventional structures and to provide, a method for producing a highly active lipid-modified
enzyme with a high yield.

[0009] Moreover, it is an object of the present invention to provide a highly reliable biosensor, which gives a low
response value (blank value) when the concentration of a substrate is zero and is capable of quantifying a substrate
with high accuracy, by the use of the lipid-modified enzyme.

Disclosure of Invention

[0010] The present invention provides a method for producing a lipid-modified enzyme comprising the steps of:
adding an enzyme to a medium containing a lipid dialkyldimethyl ammonium salt represented by the following formula
(1) so as to produce a complex of the lipid and enzyme; precipitating the produced complex; and drying the precipitate.

Cnffcrml JZH3

N + XT <1>
ChH2n+t / X CH3

EP 1 130 390 A1

wherein eech of m and n is independently an integer between 14 and 1 8, and X- is Cr, Br, I", H 2 P0 4 -, HS0 4 \

[001 "n When the enzyme is added to the medium containing the lipid, the weight ratio of enzyme to lipid is preferably
within a range of 1 :0.2 to 1:5.

s [0012] X- in the above formula (1) is preferably Cr or Br.

[0013] A biosensor of the present invention comprises: an electrically insulating base plate; an electrode system
including a working electrode and a counter electrode formed on the base plate; and a reaction layer formed on or in
the vicinity of the electrode system, wherein the reaction layer comprises at least a layer containing a liptd-modified
enzyme composed mainly of an enzyme and a lipid represented by the above formula (1), and a layer containing an

w electron mediator.

Brief Description of Drawings
[0014]

FIG. 1 is an exploded perspective view of a biosensor according to one example of the present invention, excluding
a reaction layer.

FIG. 2 is a schematic vertical sectional view of the biosensor.
20 Best Mode for Carrying Out the Invention

[0015] The following description will explain a method for producing a lipid-modified enzyme of the present invention.
[001 6] A lipid represented by the above formula (1 ) is dispersed or dissolved in a liquid, preferably water, to prepare
a lipid dispersion or lipid solution. Next, an enzyme is added to the solution. At this time, it is possible to use either of

25 a method in which the enzyme is added in the form of a solid powder and a method in which a liquid containing the
enzyme is added. The solution containing the enzyme and lipid are kept at low temperatures to precipitate a complex
of the lipid and enzyme. Next, this precipitate is separated, washed with water, and then dried to obtain a Hp.d-modif.ed
enzyme in the form of powder. Drying is performed at normal temperature or lower temperatures, and a freeze drying
method is preferably used. The most preferable medium to be used here is water. It is also possible to use organic

so solvents including alcohols such as methanol, ethanol and butanols; ethers such as ethyl ether; and acetone. S.nce
these organic solvents do not dissolve the produced lipid-modified enzyme, it is possible to read.ly separate the pro-
duced lipid-modified enzyme from the medium. „^ Q „^, mo
[0017] Here in the above formula (1), if both m and n are not greater than 13, the complex of the lipid and enzyme
to not produced or the complex is produced with a low yield. On the other hand, if both m and n are not smaller than

35 19, the lipid dispersion or lipid solution can not be prepared.

[001 8] Regarding the ratio of the enzyme and the lipid when the enzyme is added to the medium containing the lipid,
if the weight ratio of the enzyme to the lipid is within a range of 1 :0.2 to 1 .5, a yield of no less than 70% can be obtained.
[0019] The enzyme modified with the lipid is soluble in specific solvents such as benzene and toluene, but insoluble
in water. Therefore, for formation of a layer of enzyme in the biosensor, it is possible to employ a simple method in

40 which the lipid-modified enzyme is dissolved in an organic solvent, dropped on or in the vicinity of the electrodes on
the base plate, and dried. Besides, it is possible to form a layer of the water-soluble electron mediator by dropping an
aqueous solution thereof on a predetermined position and drying. Hence, if the respective layers are formed according
to such a method, inespective of the order of forming the layer containing the lipid-modified enzyme and the layer
containing the electron mediator, the enzyme and electron mediator contained in the respective layers are not affected

45 by each other, and homogeneous layers can be formed. :„„!., ho

[0020] In the present invention , examples of the enzyme modified with a lipid in the above-mentioned manner include
glucose oxidase, glucose dehydrogenase, lactate oxidase, lactate dehydrogenase, fructose oxidase, cholestero oxi-
dase, cholesterol dehydrogenase, cholesterol esterase, mutarotase, invertase, ascorbate oxidase, and alcohol oxi-

so [0021] The reaction layer of the biosensor in accordance with the present invention contains an electron mediator
as mentioned above. Examples of the electron mediator include ferricyanides, p-benzoquinone and its derrvatives
phenazine methosulfate. methylene blue, ferrocene and its derivatives. One or more than one kind of such electron
mediators are used, and it is particularly preferable to use ferricyanides.

[0022] The reaction layer of the biosensor of the present invention may contain a hydrophilic polymer as well as the
55 above-mentioned enzymes and electron mediators. The addition of a hydrophilic polymer to the reaction layer can
prevent separation of the reaction layer from the surface of the base plate or electrode system. Moreover, the addrtion
of a hydrophilic polymer has the effect of preventing clacking of the reaction layer surface, and is thus effective for
improving the reliability of the biosensor. Examples of such a hydrophilic polymer include carboxymethyl cellulose,

4

EP1 130 390 A1

hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, ethylhydroxyethyl cellulose, car-
boxymethylethyl cellulose, polyvinyl pyrrolidone, polyvinyl alcohol, polyamino acid such as polylysine, polystyrene sul-
fonate, gelatin and its derivatives, acrylic acid or its derivatives, a polymer of maleic anhydride or maleate, starch and
its derivatives. Among them, carboxymethyl cellulose is particularly preferred.
5 [0023] As the method for measuring an oxidation current, there are two types of methods: a two-e!ectrode system
using only a measuring electrode and a counter electrode; and a three-electrode system further comprising a reference
electrode, and the three-electrode system enables more accurate measurement.

[0024] The following description will explain the present invention in great detail by illustrating specific examples.

[0025] FIG. 1 is an exploded perspective view of a biosensor according to the present invention, excluding the re-
10 action layer. 1 represents an electrically insulating base plate made of polyethylene terephthalate. A silver paste is

printed on this base plate 1 by screen printing to form leads 2 and 3. Further, an electrode system including a working

electrode 4 and counter electrode 5 made from a conductive carbon paste containing a resin binder, and an electrically

insulating layer 6 made from an electrically insulating paste are formed on the base plate 1 by the same printing method.

The electrically insulating layer 6 covers the working electrode 4 and counter electrode 5 so that the exposed portion
is of the working electrode 4 and counter electrode 5 has a certain area, and also covers the leads partially.

[0026] As the materials of the leads and electrodes, while platinum, gold, palladium, etc. may be used as well as

silver and carbon, leads made from a silver paste and electrodes composed of the base made from a silver paste and

covered with a carbon paste are suitable for a disposable type biosensor

[0027] FIG. 2 is a vertical sectional view of the biosensor of the present invention.
20 [0028] A reaction layer 7 is produced by forming a first layer 7a containing an electron mediator on the electrically

insulating base plate 1 on which the electrode system is formed as shown in FIG. 1 and forming a second layer 7b

containing enzymes on the first layer 7a.

[0029] This biosensor is assembled by the insulating base plate 1 made of polyethylene carbonate, a cover 9, and
a spacer 8 sandwiched between the base plate 1 and the cover 9. These members are adhered together in a positional

25 relationship as shown by the broken lines of FIG. 1 so as to construct the biosensor.

[0030] The spacer 8 has a slit 1 0 that forms a sample solution supply path, and an air vent 11 is formed in the cover
9. When the base plate 1 and the cover 9 are layered and adhered together with the spacer 8 therebetween, a cavity
serving as the sample supply path is formed in the section of the slit 10 between the base plate 1 and cover 9. In this
cavity, the open end of the slit 10 as the beginning end serves as a sample solution supply opening, and the final end

30 js connected to the air vent 11 .

[0031 ] Here, while a cover member is constructed by a combination of the cover 9 and spacer 8, it may be constructed
by a single member provided with a groove equivalent to the slit 10 of the spacer 8. In a biosensor constructed by
combining the insulating base plate with the cover member that forms the sample solution supply path between the
base plate and the cover member as described above, it is not necessarily to form the reaction layer on the electrode

35 system. The reaction layer needs to be formed at a position where it is exposed to the sample solution supply path
and dissolved in the sample solution before the sample solution reaches the electrode system through the sample
supply path by capillarity.

Example 1

40

[0032] An aqueous solution of potassium ferricyanide was dropped on the electrode system on the base plate 1 of
FIG. 1 and dried to form the first layer 7a. The amount of potassium ferricyanide contained in this first layer 7a was 1 .
mg per square centimeter.

[0033] Next, a layer of an enzyme modified with a lipid was formed on the first layer 7a as follows.

45 [0034] First, the lipid-modified enzyme was produced by the following method. 10 mg of lipid dioctadecyldimethyl
ammonium chloride represented by the formula (1), wherein m=1 8 and n=1 8, was mixed with 1 0 ml of deionized water,
and the lipid was dispersed in the deionized water by using an ultrasonic washer. 10 mg of glucose oxidase (EC1 .1 .3.4:
hereinafter referred to as "GOD") was dissolved in this dispersion. After cooling the resultant solution in an ice bath
for two hours, it was cooled in a refrigerator for 24 hours. As a result of this cooling, a complex of the lipid and enzyme

50 was precipitated and deposited. After separating this precipitate and washing it with deionized water, it was dried using
a freeze-drier. In this manner, the lipid-modified enzyme in the form of powder was obtained. The yield was 99%, and
the ratio of the enzyme protein in the lipid-modified enzyme was 50% by weight.

[0035] Next, the powder of the lipid-modrfied enzyme was dissolved in toluene, and the resultant solution was dropped
on the above-mentioned first layer 7a and dried to form the second layer 7b. At this time, the layer of the lipid-modified
55 enzyme was formed in such a state that it was completely separated from the previously formed layer of potassium
ferricyanide. The amount of lipid-modified enzyme contained in this second layer 7b was 0.2 mg per square centimeter
of the reaction layer.

[0036] When a sample solution containing glucose is supplied to the reaction layer 7, the glucose in the sample

5

EP1 130 390 A1

solution is oxidized by the GOD. Then, simultaneously with the oxidation, the electron mediator in the reaction layer
is reduced. Subsequently, after a passage of one minute from the supply of the sample solution, a voltage of +0.5 V
was applied to the working electrode 4 based on the counter electrode 5 to oxidize the reductant of the electron mediator.
Further, five seconds later, the current value was measured. Since the current value is proportional to the concentration
5 of the generated electron mediator, i.e., the concentration of the substrate in the sample solution, it is possible to obtain
the glucose concentration in the sample solution by measuring this current value.

[0037] Samples with glucose concentrations, of 0, 1 80, 360 and 540 mg/dl were prepared, and the response current
value of the sensor was measured for the respective samples, and the results of the measurements showed that
response current value and the glucose concentration had a certain correlation as shown in Table 1 and exhibited good
w linearity. Further, the blank value was 0 uA.

Example 2

[0038] In the same manner as in Example 1 , the first layer 7a containing potassium ferricyanide was formed.
15 [0039] Next, a lipid-modified enzyme was produced by the same method as in Example 1. In this case, 10 mg of
lipid dioctadecyldimethyl ammonium chloride represented by the formula (1 ), wherein m=1 8 and n=1 8,10 ml of deion-
ized water and 5 mg of GOD were used. At this time, the yield of the lipid-modified enzyme was 90%, and the ratio of
the enzyme protein in the lipid-modified enzyme was 37% by weight.

[0040] The second layer 7b containing the lipid-modified enzyme thus obtained was formed. The amount of lipid-
20 modified enzyme contained in this second layer 7b was 0.3 mg per square centimeter of the reaction layer.

[0041] The response current value of the sensor with respect to a glucose standard solution was measured by the
same method as in Example 1, and the response current value exhibited good linearity with respect to the glucose
concentration as the result of the measurement. Further, the blank value was 0 uA.

25 Example 3

[0042] In the same manner as in Example 1, the first layer 7a containing potassium ferricyanide was formed.
[0043] Next, a lipid-modified enzyme was produced by the same method as in Example 1. In this case, 10 mg of
lipid dioctadecyldimethyl ammonium chloride represented by the formula (1 ), wherein m=1 8 and n=1 8, 1 0 ml of deion-
30 ized water and 2 mg of GOD were used. At this time, the yield of the lipid-modified enzyme was 82%, and the ratio of
the enzyme protein in the lipid-modified enzyme was 20% by weight.

[0044] The second layer 7b containing the lipid-modified enzyme thus obtained was formed. The amount of lipid-
modified enzyme contained in this second layer 7b was 0.5 mg per square centimeter of the reaction layer.
[0045] The response current value of the sensor with respect to the glucose standard solution was measured by the
35 same method as in Example 1, and the response current value exhibited good linearity with respect to the glucose
concentration as the result of the measurement. Further, the blank value was 0 uA.

Example 4

40 [0046] In the same manner as in Example 1 , the first layer 7a containing potassium ferricyanide was formed.

[0047] Next, a lipid-modified enzyme was produced by the same method as in Example 1 . In this case, 5 mg of lipid
dioctadecyldimethyl ammonium chloride represented by the formula, (1), wherein m=18 and n=18, 10 ml of deionized
water and 1 0 mg of GOD were used. At this time, the yield of the lipid-modified enzyme was 85%, and the ratio of the
enzyme protein in the lipid-modified enzyme was 60% by weight.

45 [0048] The second layer 7b containing the lipid-modified enzyme thus obtained was formed. "The amount of lipid-
modified enzyme contained in this second layer 7b was 0.2 mg per square centimeter of the reaction layer.
[0049] The response current value of the sensor with respect to the glucose standard solution was measured by the
same method as in Example 1, and the response current value exhibited good linearity with respect to the glucose
concentration as the result of the measurement. Further, the blank value was 0 uA.

50

Example 5

[0050] In the same manner as in Example 1 , the first layer 7a containing potassium ferricyanide was formed.
[0051] Next, a lipid-modified enzyme was produced by the same method as in Example 1 , In this case, 2 mg of lipid
55 dioctadecyldimethyl ammonium chloride represented by the formula (1 ), wherein m=1 8 and n=1 8, 1 0 ml of deionized
water and 10 mg of GOD were used. At this time, the yield of the lipid-modified enzyme was 70%, and the ratio of the
enzyme protein in the lipid-modified enzyme was 76% by weight.

[0052] The second layer 7b containing the lipid-modified enzyme thus obtained was formed. The amount of lipid-

6

EP1 130 390 A1

modified enzyme contained in this second layer 7b was 0.1 5 mg per square centimeter of the reaction layer.
[0053] The response current value of the sensor with respect to the glucose standard solution was measured by the
same method as in Example 1 , and the response current value exhibited good linearity with respect to the glucose
concentration as the result of the measurement. Further, the blank value was 0 uA.

5

Comparative Example 1

[0054] In order to confirm the effect of lipid modification of the lipid-modified enzyme described in Example 1, the
response characteristic and blank value of a sensor using an enzyme that was not modified with a lipid were evaluated.

10 A mixed aqueous solution of potassium ferricyanide and GOD was dropped on the electrode system on the base plate
1 of FIG. 1 and dried to form the reaction layer 7. The amount of potassium ferricyanide contained in this layer 7 was
1 mg per square centimeter of the reaction layer, and the amount of the GOD was 0.1 mg. Since the mixed layer of
potassium ferricyanide and GOD was formed for the first layer, the second layer was not formed.
[0055] Next, the response current value of the sensor was measured by the same method as in Example 1 . As a

15 result, the response current value and the glucose concentration had a certain correlation and exhibited good linearity.
This response linearity was almost the same as that shown in Example 1. However, the blank value was 0.1 uA
[0056] Table 1 shows a comparison between the response characteristics of the sensor of Example 1 using the lipid-
modified enzyme and the sensor of Comparative Example 1 using an unmodified enzyme.

[0057] Next, after storing the sensor of Example 1 and the sensor of Comparative Example 1 in a dried state at 50° C
20 for one month, the blank value was measured in the same manner as above. As a result, with the sensor of Comparative
Example 1 using the unmodified enzyme, the blank value was increased to 0.2 uA On the other hand, with the sensor
of Example 1 using the lipid-modified enzyme, the blank value was 0.05 pA.

Table 1

30

Response current value (\iA)

Glucose concentration (mg/dl)

0

180

360

540

Example 1

0.0

6.1

12.0

18.7

Comparative Example 1

0.1

5.7

12.0

18.3

Comparative Example 2

[0058] According to the same method as in Example 1, a lipid-modified enzyme was produced using 10 mg of lipid
didodecyldimethyl ammonium bromide represented by the formula (1), wherein m=12 and n=12, 10 ml of deionized
water and 10 mg of GOD. The yield of the lipid-modified enzyme was not greater than 20%, and the ratio of the enzyme
protein in the lipid-modified enzyme was 41 % by weight.

[0059] Lipid-modified enzymes were produced in the same manner as in Example 1 using lipids having different
values of m and n in the formula (1) and 10 mg of enzyme, and the yields and the ratio of the enzyme protein in the
respective lipid-modified enzymes were compared as shown in Table 2.

Table 2

m

n

Yield (wt.%)

Ratio of enzyme protein (wt.%)

12

12

25

44

14

14

82 .

57

16

16

88

70

18

18

99

50

[0060] While glucose sensors using glucose oxidase as the enzyme are explained in the above examples, the present
invention is also applicable in the same manner to enzymes for use in various sensors, such as lactic acid sensor,
cholesterol sensor, fructose sensor, sucrose sensor, alcohol sensor, and ascorbic acid sensor.

Industrial Applicability

[0061 ] As described above, according to the present invention, it is possible to obtain a biosensor capable of rapidly

7

10

15

20

25

30

35

40

45

EP 1 130 390 A1

and readily quantifying a substrate contained in samples such as biological samples, like blood and urine, and raw
materials and products used in the food industry, with high accuracy.

5 Claims

1 . A method for producing a lip id-modified enzyme comprising the steps of:

adding an enzyme to a medium containing a lipid represented by the following formula (1),

Cnrffcm+I JZ\\ 3

H* X" d)

CnH2n+i / X CH3

wherein each of m and n is independently an integer between 1 4 and 1 8, and X- is CI-, Br, l\ H 2 PCV HSO -
or N0 3 -, so as to produce a complex of the lipid and enzyme; ' ' 4 *

precipitating said produced complex; and
drying said precipitate.

2. The method for producing a lipid-modified enzyme as set forth in claim 1 ,

wherein a weight ratio of said enzyme and lipid in said medium is within a range of 1 :0.2 to 1 :5.

3. The method for producing a lipid-modified enzyme as set forth in claim 1 ,

wherein X- in the formula (1) is Cr or Br.

4. A biosensor comprising:

an electrically insulating base plate;

an electrode system including a working electrode and a counter electrode formed on said base plate; and
a reaction layer formed on or in the vicinity of said electrode system,

wherein said reaction layer comprises at least a layer containing a lipid-modified enzyme composed mainly
of an enzyme and a lipid represented by the following formula (t),

CmH2rm1 ^3

N* X" n>
CnH2ri+i /. X CH3

and a layer containing an electron mediator.

50 5. The biosensor as set forth in claim 4,

wherein X- in the formula (1) is CI- or Br.

8

EP1 130 390 A1

FIG.1

EP1 130 390 A1

EP1 130 390 A1

INTERNATIONAL SEARCH REPORT

International application No.

PCT/JPOO/06111

A. CLASSIFICATION OF SUBJECT MATTER

Int. CI 1 G01N27/447 C12Q1/00 C12N9/O0

According to International Patent Classification (IPC) or to both national classification and IPC

B. FIELDS SEARCHED

Minimum documentation searched (classification system followed by classification symbols)
Int. CI 7 G01N27/447 C12Q1/00 C12N9/00

Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched
Jitsuyo Shi nan Koho 1922-1996 Toroku Jiteuyo Shinan Koho 1994-2000

Kokai Jitsuyo Shinan Koho 1971-2000 Jitsuyo Shinan Toroku Koho 1996-2000

Electronic data base consulted during the international search (name of data base and, where practicable, search terms used)
JOIS: LIPID- MODIFIED ENZYME* ELECTRONE, LIPID* COMPLEX* ENZYME* ELECTRODE
CA(STN) : CONSTITUTIONAL FOMULA* ENZYME?

(in Japanese)

C DOCUMENTS CONSIDERED TO BE RELEVANT

Category*

Citation of document, with indication, where appropriate, of the relevant passages

Masato TOMINAGA, Satoko KUSANO, Naotoshi NAKASHIMA,
Bioelectrochem. Bioenerg., 42(1) pp. 59-62 (1997)

US, 5658443, A (MATSUSITA ELECTRIC INDUSTRIAL Co . , Ltd.) ,

19 August, 1997 (19.08.97),

Columns 10 to 11, EXAMPLE 4 & EXAMPLE 5

& JP, 07-083872, A

Relevant to claim No.

1-5

1-5

{ ) Further documents are listed in the continuation of Box C Q See patent family

* Special categories of cited documents:

"A* document defining the general state of the art which is not

considered to be of particular rclevmce
*E" earlier document but published on or after the international filing

date

"V document which may throw doubts on priority claim(i) or which is
cited to establish the publication date of another citation or other
special reason (as specified)

"O* document referring to an oral disclosure, use, exhibition or other

T* document published prior to the international filing date but later
than the priority date claimed

T* later document published after the international fding date or
priority date and not in conflict with the application but cited to
understand die principle or theory underlying the invention

"X" document ofparticular relevance; the claimed invention cannot be
considered novel or cannot be considered to involve an inventive
step when the document is taken alone

"Y* document ofparticular rdcvinoc; the claimed invention cannot be
considered to involve an inventive step when the document is
combined with one or more other such documents, such
combination being obvious to a person skilled in the art
document member of the same patent family

Date of the actual completion of the international search
27 September, 2000 (27.09.00)

Date of mailing of the international search report
10 October, 2000 (10.10.00)

Name and mailing address of the ISA/
Japanese Patent Office

Facsimile No.

Authorized officer
Telephone No.

Form PCT/ISA/210 (second sheet) (July 1992)

11

k ■

r

V

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